The referenced U.S. Pat. No. 4,266,447, the disclosure of which is hereby incorporated by reference, describes apparatus and method to control an automotive-type stepped transmission, in which the torque supplied by the engine is reduced during gear change. This reduction in supplied power can be obtained by reducing fuel supply or, for example, adjusting ignition timing, typically in retardation direction. Reducing the fuel supply during gear shifting permits particularly soft and smooth engagement of gears, and thus reduces shifting jolts.
Various types of drive trains of automotive vehicles include systems in which the engine speed is sensed; and, additionally, the direction of power transfer within the drive train is determined. If the power is from the engine to the driven wheels through the transmission, the engine is controlled to operate in accordance with traffic requirements, as commanded by the operator. If the transfer of power, however, is in the reverse direction, for example upon coasting downhill, under engine braking conditions, or the like, collectively and usually referred to as "overrunning" condition of the vehicle and drive train, a signal 13s can be developed indicating this overrunning condition. Based on this signal, and to save fuel and not operate the engine at speeds which may be determined by the engaged gear, the torque output of the engine can be reduced based on such sensed signal.